The landscape of somatic mutation in sporadic Chinese colorectal cancer.
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ABSTRACT:
SUBMITTER: Liu Z
PROVIDER: S-EPMC6007951 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Colorectal cancer (CRC) is the fifth leading cause of cancer-related death in China. The incidence of Chinese CRC has increased dramatically with the changes of dietary and lifestyle. However, the genetic landscape of Chinese colorectal cancer mutation is still poorly understood. In this study, we have performed whole exome-sequencing analysis of 63 CRC cases. We found that Chinese CRC were hypermutated, which were enriched in ECM-receptor interaction, antigen processing and presentation, and focal adhesion. Analysis with clinical characteristics indicated that the deficiency of CRC driver gene, FCGBP and NBPF1 conferred CRC development and was showed worse survival rates, which could be the novel regulators and, diagnostic and prognostic biomarkers for Chinese CRC. Taken together, the application of whole exome-sequencing unveiled previously unsuspected somatic mutation landscape in Chinese CRCs, which may expand the understanding of disease mechanisms and provide an alternative personalized treatment for Chinese CRC patients.
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Project description:OBJECTIVE:There are few studies which characterised the molecular alterations in premalignant colorectal adenomas. Our major goal was to establish colorectal adenoma genome atlas and identify molecular markers of progression from colorectal adenoma to adenocarcinoma. DESIGN:Whole-exome sequencing and targeted sequencing were carried out in 149 adenoma samples and paired blood from patients with conventional adenoma or sessile serrated adenoma to characterise the somatic mutation landscape for premalignant colorectal lesions. The identified somatic mutations were compared with those in colorectal cancer (CRC) samples from The Cancer Genome Atlas. A supervised random forest model was employed to identify gene panels differentiating adenoma from CRC. RESULTS:Similar somatic mutation frequencies, but distinctive driver mutations, were observed in sessile serrated adenomas and conventional adenomas. The final model included 20 genes and was able to separate the somatic mutation profile of colorectal adenoma and adenocarcinoma with an area under the curve of 0.941. CONCLUSION:The findings of this project hold potential to better identify patients with adenoma who may be candidates for targeted surveillance programmes and preventive interventions to reduce the incidence of CRC.
| S-EPMC6031265 | biostudies-literature
Project description:KRAS is an independent negative predictor for anti-epidermal growth factor receptor (anti-EGFR) treatment in colorectal cancers (CRCs). However, 30% to 50% of CRC patients are KRAS-positive and do not benefit from anti-EGFR therapy. In this study, we investigated the mutational features and clinical significance of KRAS-positive Chinese CRC patients. A total of 139 Chinese CRC patients who received clinical KRAS testing (Sanger sequencing) were examined by immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH). Fifty KRAS-positive specimens were further detected by next-generation sequencing (NGS). The most prevalent mutation in KRAS was G12D (46%), followed by G12V (20%), and G13D (18%). In addition to KRAS, 72 unique alterations in another 12 genes were also detected. The most common mutated genes were TP53 (62%), APC (46%), and PIK3CA (22%). The proportion of HER2 amplifications in KRAS-positive CRC patients was 4.4%, which was lower than that in KRAS -negative CRC patients (14.3%). No relationship was found between HER2 amplification and KRAS status (p = 0.052). However, the odds ratio is very low (0.279). In addition, these gene mutations were not significantly associated with age, sex, tumor size, lymph node metastasis, mismatch repair-deficient, or tumor differentiation. However, TP53 mutations were more prevalent in colon cancer with KRAS mutations than in rectal cancer (75.0% vs 28.6%, respectively, p = 0.004). The negative predictive value of the IHC analysis for predicting HER2 amplification reached to 98.39%, while the positive predictive value reached only 50%. Overall, the mutation profiling of Chinese CRC patients with KRAS mutations is different from that of Western CRC patients. Our results will help us to understand the molecular features of Chinese CRC patients.
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Project description:Neurofibromatosis type 1 (NF1: Online Mendelian Inheritance in Man (OMIM) #162200) is an autosomal dominantly inherited tumour predisposition syndrome. Heritable constitutional mutations in the NF1 gene result in dysregulation of the RAS/MAPK pathway and are causative of NF1. The major known function of the NF1 gene product neurofibromin is to downregulate RAS. NF1 exhibits variable clinical expression and is characterized by benign cutaneous lesions including neurofibromas and café-au-lait macules, as well as a predisposition to various types of malignancy, such as breast cancer and leukaemia. However, acquired somatic mutations in NF1 are also found in a wide variety of malignant neoplasms that are not associated with NF1.Capitalizing upon the availability of next-generation sequencing data from cancer genomes and exomes, we review current knowledge of somatic NF1 mutations in a wide variety of tumours occurring at a number of different sites: breast, colorectum, urothelium, lung, ovary, skin, brain and neuroendocrine tissues, as well as leukaemias, in an attempt to understand their broader role and significance, and with a view ultimately to exploiting this in a diagnostic and therapeutic context.As neurofibromin activity is a key to regulating the RAS/MAPK pathway, NF1 mutations are important in the acquisition of drug resistance, to BRAF, EGFR inhibitors, tamoxifen and retinoic acid in melanoma, lung and breast cancers and neuroblastoma. Other curiosities are observed, such as a high rate of somatic NF1 mutation in cutaneous melanoma, lung cancer, ovarian carcinoma and glioblastoma which are not usually associated with neurofibromatosis type 1. Somatic NF1 mutations may be critical drivers in multiple cancers. The mutational landscape of somatic NF1 mutations should provide novel insights into our understanding of the pathophysiology of cancer. The identification of high frequency of somatic NF1 mutations in sporadic tumours indicates that neurofibromin is likely to play a critical role in development, far beyond that evident in the tumour predisposition syndrome NF1.
| S-EPMC5480124 | biostudies-literature
Project description:BackgroundMost colorectal cancers (CRC) arise from precursor lesions. This study aimed to characterize the mutation profile of colorectal cancer precursor lesions in a Brazilian population.MethodsIn total, 90 formalin-fixed paraffin-embedded colorectal precursor lesions, including 67 adenomas, 7 sessile serrated lesions, and 16 hyperplastic polyps, were analyzed by next-generation sequencing using a panel of 50 oncogenes and tumor suppressor genes. The genetic ancestry of the patients was estimated.ResultsSomatic driver mutations were identified in 66.7% of cases, including alterations in APC (32.2%), TP53 (20.0%), KRAS (18.9%), BRAF (13.3%) and EGFR (7.8%). Adenomas displayed a higher number of mutations, mainly in APC, compared to serrated polyps (73.1% vs. 47.8%, p = 0.026). Advanced adenomas had a significantly higher frequency of mutation in KRAS and a high overall mutation rate than early adenomas (92.9% vs. 59%, p = 0.006). A high degree of ancestry admixture was observed in the population studied, with a predominance of European components (mean of 73%) followed by African (mean of 11.3%). No association between genetic ancestry and type of lesions was found. The mutation profile of Brazilian colorectal precursor lesions exhibits alteration in APC, KRAS, TP53, and BRAF at different frequencies according to lesion type.ConclusionsThese results bestow the knowledge of CRC's biologic history and support the potential of these biomarkers for precursor lesions detection in CRC screening of the Brazilian population.
| S-EPMC9238170 | biostudies-literature
Project description:BACKGROUND:Somatic mutations in healthy tissues contribute to aging, neurodegeneration, and cancer initiation, yet they remain largely uncharacterized. RESULTS:To gain a better understanding of the genome-wide distribution and functional impact of somatic mutations, we leverage the genomic information contained in the transcriptome to uniformly call somatic mutations from over 7500 tissue samples, representing 36 distinct tissues. This catalog, containing over 280,000 mutations, reveals a wide diversity of tissue-specific mutation profiles associated with gene expression levels and chromatin states. For example, lung samples with low expression of the mismatch-repair gene MLH1 show a mutation signature of deficient mismatch repair. In addition, we find pervasive negative selection acting on missense and nonsense mutations, except for mutations previously observed in cancer samples, which are under positive selection and are highly enriched in many healthy tissues. CONCLUSIONS:These findings reveal fundamental patterns of tissue-specific somatic evolution and shed light on aging and the earliest stages of tumorigenesis.
| S-EPMC6930685 | biostudies-literature
Project description:Breast cancer (BC) is a genetically heterogeneous disease with high prevalence in Northern Europe. However, there has been no detailed investigation into the Scandinavian somatic landscape. Here, in a homogeneous Swedish cohort, we describe the somatic events underlying BC, leveraging a targeted next-generation sequencing approach. We designed a 20.5 Mb array targeting coding and regulatory regions of genes with a known role in BC (n = 765). The selected genes were either from human BC studies (n = 294) or from within canine mammary tumor associated regions (n = 471). A set of predominantly estrogen receptor positive tumors (ER + 85%) and their normal tissue counterparts (n = 61) were sequenced to ~ 140 × and 85 × mean target coverage, respectively. MuTect2 and VarScan2 were employed to detect single nucleotide variants (SNVs) and copy number aberrations (CNAs), while MutSigCV (SNVs) and GISTIC (CNAs) algorithms estimated the significance of recurrent somatic events. The significantly mutated genes (q ≤ 0.01) were PIK3CA (28% of patients), TP53 (21%) and CDH1 (11%). However, histone modifying genes contained the largest number of variants (KMT2C and ARID1A, together 28%). Mutations in KMT2C were mutually exclusive with PI3KCA mutations (p ≤ 0. 001) and half of these affect the formation of a functional PHD domain. The tumor suppressor CDK10 was deleted in 80% of the cohort while the oncogene MDM4 was amplified. Mutational signature analyses pointed towards APOBEC deaminase activity (COSMIC signature 2) and DNA mismatch repair (COSMIC signature 6). We noticed two significantly distinct patterns related to patient age; TP53 being more mutated in the younger group (29% vs 9% of patients) and CDH23 mutations were absent from the older group. The increased somatic mutation prevalence in the histone modifying genes KMT2C and ARID1A distinguishes the Swedish cohort from previous studies. KMT2C regulates enhancer activation and assists tumor proliferation in a hormone-rich environment, possibly pointing to a role in ER + BC, especially in older cases. Finally, age of onset appears to affect the mutational landscape suggesting that a larger age-diverse population incorporating more molecular subtypes should be studied to elucidate the underlying mechanisms.
| S-EPMC7653953 | biostudies-literature
Project description:ObjectivesRoughly half of hereditary nonpolyposis colorectal cancer (HNPCC) cases are Lynch syndrome and exhibit germ-line mutations in DNA mismatch repair (MMR) genes; the other half are familial colorectal cancer (CRC) type X (FCCTX) and are MMR proficient. About 70% of Lynch syndrome tumors have germ-line MLH1 or MSH2 mutations. The clinical presentation, histopathological features, and carcinogenesis of FCCTX resemble those of sporadic MMR-proficient colorectal tumors. It is of interest to obtain biomarkers that distinguish FCCTX from sporadic microsatellite stable (MSS) CRC, to develop preventive strategies.MethodsThe tumors and adjacent normal tissues of 40 patients with HNPCC were assayed using the Illumina Infinium HumanMethylation27 (HM27) BeadChip to assess the DNA methylation level at about 27,000 loci. The germ-line mutation status of MLH1 and MSH2 and the microsatellite instability status in these patients were obtained. Genome-wide DNA methylation measurements of three groups of patients with general CRC were downloaded from public domain databases. Probes with DNA methylation levels that differed significantly between patients with sporadic MSS CRC and FCCTX were examined, to explore their potential as biomarkers.ResultsWe found that MSS HNPCC tumors were overwhelmingly hypomethylated compared with those from patient groups with other types of CRC, including germ-line MLH1/MSH2-mutated HNPCC and sporadic MSS CRC. Five gene-marker panels that exhibited a sensitivity of 100% and a specificity higher than 90% in both discovery and validation cohorts were proposed to distinguish MSS HNPCC tumors from sporadic MSS CRC.ConclusionsOur results warrant further investigation and validation. The loci identified here may become useful biomarkers for distinguishing between FCCTX and sporadic MSS CRC tumors.
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Project description:Microsatellite instability (MSI) is characteristic of hereditary nonpolyposis colorectal cancer, and occurs in a subset (10 to 15%) of unselected colorectal cancer cases. In hereditary nonpolyposis colorectal cancer, MSI is caused by defects in five mismatch repair genes, and in sporadic cases the main cause seems to be somatic MLH1 promoter methylation. Most likely additional hereditary nonpolyposis colorectal cancer genes remain to be discovered. Genes with simple repeats in their coding region are often targets for deletions in MSI-positive tumors. Several genes (TGFbeta RII, IGFIIR, MSH3, MSH6, BAX, MBD4) with significance in tumorigenesis harbor repeats in their coding regions and are often somatically inactivated because of deletions causing frameshifts. Recently, a novel human mismatch repair gene, MLH3, was cloned and shown to be involved in mammalian mismatch repair. To evaluate the possible role of MLH3 in hereditary cancer, we performed germline single-strand conformation polymorphism-analysis for 52 patients displaying features of inherited colorectal cancer. Forty-six of these had been diagnosed with MSI-positive tumors. No germline mutations were found. Similar to MSH3 and MSH6, MLH3 harbors mononucleotide repeats, ie, (A(6))-(A(9)), in its coding region, which makes it a putative target for somatic mutations in MSI-positive tumors. To evaluate its somatic inactivation we performed a deletion search focusing on eight exonic MLH3 mononucleotide repeats in a series of 93 MSI-positive tumors. Somatic deletions were found in 8.6% of the samples, a frequency similar to one detected in neutral noncoding mononucleotide repeats. No evidence of involvement of MLH3 in MSI tumorigenesis was obtained.
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Project description:Recent genomic studies suggest that Asian breast cancer (BC) may have distinct somatic features; however, most comparisons of BC genomic features across populations did not account for differences in age, subtype, and sequencing methods. In this study, we analyzed whole-exome sequencing (WES) data to characterize somatic copy number alterations (SCNAs) and mutation profiles in 98 Hong Kong BC (HKBC) patients and compared with those from The Cancer Genome Atlas of European ancestry (TCGA-EA, N = 686), which had similar distributions of age at diagnosis and PAM50 subtypes as in HKBC. We developed a two-sample Poisson model to compare driver gene selection pressure, which reflects the effect sizes of cancer driver genes, while accounting for differences in sample size, sequencing platforms, depths, and mutation calling methods. We found that somatic mutation and SCNA profiles were overall very similar between HKBC and TCGA-EA. The selection pressure for small insertions and deletions (indels) in GATA3 (false discovery rate (FDR) corrected p < 0.01) and single-nucleotide variants (SNVs) in TP53 (nominal p = 0.02, FDR corrected p = 0.28) was lower in HKBC than in TCGA-EA. Among the 13 signatures of single-base substitutions (SBS) that are common in BC, we found a suggestively higher contribution of SBS18 and a lower contribution of SBS1 in HKBC than in TCGA-EA, while the two APOBEC-induced signatures showed similar prevalence. Our results suggest that the genomic landscape of BC was largely very similar between HKBC and TCGA-EA, despite suggestive differences in some driver genes and mutational signatures that warrant future investigations in large and diverse Asian populations.
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